Thermostatic control and indicating device



April 19, 1949. P. R. LEE 2,467,896

THERMOSTATIC CONTROL AND INDICATING DEVICE Filed May 5G, 1942 3Sheets-Sheet l 2z I Z/ WITNESSES: INVENTOR d Pau/E ee April 19, 1949.

Filed May 30, 1942 P. R. LEE

THERMOSTATIC CONTROL AND INDICATING DEVICE 3 Sheets-Sheet 2 INVENTORPau/E. 66.

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'ATTONEY April 19, 1949. R LEE 2,467,896

THERMOSTATIC CONTROL AND INDICATING DEVICE vFiled May 30, 1942 3Sheets-Sheet 3 z i i FI' .,9; I -A y' C l if B /7 l a a I I l 1 l 1 l ml .E l l l k 1 l l l l I l l l WITNESSES: INVENTOR p00/ E. L.

Patented Apr. 19, 1949 .THERMOSTATIC CONTROL AND INDICATIN G DEVIC PaulR. Lee, Mansfield, Ohio, assignor to Westinghouse Electric Corporation,

East Pittsburgh,

a corporation of Pennsylvania.

Application May 30, 1942, Serial No. 445,165

1 Claim. 1

My invention relates to electrically heated appliances, and moreparticularly to temperature control and indicating devices for suchappliances.

While the invention embodied herein is particularly adapted for use withelectrical appliances and is described as being applied to anelectrically heated roaster, it will be apparent to those skilled in theart that its use is not limited to such an application.

Electrically heated roasters and other appliances have utilized manuallyadjustable thermostats for selectively determining the temperature ofoperation of such devices. In addition, indicating devices have beenassociated with the thermostat and heating element to indicate variousphases of energization of the device. However, in no case has there beena thermostatic structure which embodies control features for operating asignaling means which would indicate when the device being controlled isconnected to a suitable power supply and an additional signaling meansfor indicating when the device is at or within the determinedtemperature range, as selected by an operator.

It is therefore an object of my invention to provide a thermostaticstructure embodying circuit control means for operating a signal so asto indicate when the device is connected to a suitable power supply, aswell as control means for indicating when the device is below itspredetermined operating temperature and when above its operatingtemperature.

A further object of my invention is to provide a thermostatic structurewith an auxiliary make and break circuit-controlling device which isactuated by the thermostatic control adjusting means so as to actuate asignal when the thermostat is turned to an on position, providing thereis a suitable power supply associated therewith.

Another object of my invention is to provide a thermostat vfor anelectrical roaster, or the like, embodying a thermally responsiveelement which flexes with changes in temperature of the device so as toregulate the power supplied to the heating element of said device and toactuate control means for energizing a signal to indicate that thedevice is at its proper temperature.

Still a further object of my invention is to provide a thermostat for anelectrical roaster, or the like, having an auxiliary or secondcontactcarrying arm positioned intermediate a thermally responsiveelement and a main contact arm so as to be moved into engagement withthe main contact arm, prior to any movement of said contact arm, toenergize a signal to indicate that the roaster device, or the like, hasarrived at the predetermined selected operating temperature.

Still another object of my invention is to provide a thermostat for aroaster, or the like, having an auxiliary contact structure engageableby the main contact arm so as to interrupt a signal circuit to indicatewhen the roaster temperature is above the predetermined set value.

Other objects of my invention will either be pointed out specifically inthe course of the iollowing description of the device embodying myinvention, or will be apparent from such description, reference beingmade to the accompanying drawings, in which:

Figure 1 is a top plan view of a thermostat embodying my invention withthe cover removed therefrom;

Fig. 2 is a View taken along the line II-II of Fig. 1 with the cover inposition;

Fig. 3 is a bottom view of the thermostatic structure shown in Fig. 1;

Figs.l 4 and 5 are sectional views taken along the lines IV-IV and V-Vof Fig. 1, respectively;

Fig. 6 is a sectional View, taken along the line VI-VI of Fig. 1,indicating the movable parts of the thermostat in its cold or initialoperating position;

Fig.` 7 is a view similar to Fig. 6 with the movable operating parts ofthe thermostat in its fully heated or deenergized position;

Fig. 8 is an end view of a roaster partially in section having thethermostatic structure embodying my invention associated therewith;

Fig. 9 is a time-temperature curve illustrating the temperaturecharacteristics of a controlled device, such as a roaster, and theoperation of the signals embodying my invention; and

Fig. 10 is a schematic wiring diagram illustrating a thermostatembodying my invention associated with a roaster or the like.

Referring to the accompanying drawings, in which like referencecharacters indicate like parts in the several drawings, there is shown athermostatic structure lilv which has been designed primarily foroperation with a roaster structure. However, said thermostatic structurei0 and the sub-combinations thereof may be used with or in any otherdesired device. It will be noted from the accompanying drawings that Ihave not illustrated a roaster per se (except in Fig. 8), inasmuch as itis believed unnecessary to include all the parts of such a structure inthe drawings. However, it is to be understood that the said thermostatis primarily adapted for use within a roaster structure, or the like.

The thermostat I embodying my invention is primarily an improvement overthe thermostatic structure disclosed and claimed in a copendingapplication of E. K. Clark and P. R. Lee, Serial No. 206,329, filed May6, 1938, and assigned to the assignee of this invention, which issued asPatent No. 2,298,928 on October 13, 1942. The

thermostat disclosed therein may be generally described as follows:

A substantially horizontal support II having upstanding sides IIa has abimetallic element member I2 fulcrumly positioned thereupon by means ofa fulcrum I3 which is rigidly attached to said support. An adjustingscrew I4 having an undercut portion I5 within its inner end is adaptedto fit within a notched or cutout portion of one end of the bimetallieelement I2 whereby said adjusting screw I4 may change the angularposition of said thermal responsive element I2 so as to vary itsoperating characteristics. The free end of said bimetalllc element I2has rigidly attached thereto an insulating buttonlike member IB which isadapted to engage other working parts of the thermostat to control theenergization of the circuit passing therethrough. A. main contact arm I1is rigidly attached by means of one end thereof to the support II bymeans of an upstanding supporting member I8 and carries upon its otherend a main movable contact I9. In addition, a flexible current-carryingmember 28 is folded back over the arm I2 to carry the greater portion ofcurrent ilowing through the thermostat I0. This flexible member 2D isattached to the arm support I8 at one end and to the main movablecontact I9 at its other end. Suitable terminal mem-bers 2| and 22 arerigidly attached to both the main arm support member I8 and to astationary contact support 23, respectively, to provide means forconnecting the thermostat III in series with the roaster heating element24 (see Figs. 8 and 10). This type of thermostat, as set forth in theaboveidentified patent, may be positioned within a roaster structure (asin Fig. 8) so as to maintain the temperature thereof in keeping withestablished practice. Specifically, as the temperature increases, thebimetallic thermal responsive element I2 fiexes upwardly, whereby theinsulating button I6 Vpositioned upon the free end thereof engages themain arm I1 intermediate its ends so as to bodily move said arm I1 anddisengage the cooperating main contacts I9 and 23 so as to deenergizethe roaster, or the like.

In order to provide suitable signaling means to indicate when theroaster structure, or the like, is energized and to indicate when suchstructure is at its preselected temperature, I utilize the followingstructures.

A power-on signal 25 (see Fig. 1) is energized through a switch springmember 26 rigidly attached at one end thereof to a side IIa of thethermostatic support or housing II by means oi' a suitable rivetstructure 21. A movable contact 28 is rigidly attached to the free endof said switch member 26 so as to engage a stationary contact 29 rigidlyattached to the support II.

The switch spring 26 is adapted to bias the mov- :arm terminal 22 andsupport I8 at one end and 4 the rigid and stationary end oi' the switchspring 26 at its other end. This provides a circuit from the powerterminal 22 of the main contact ing screw i4 is moved to a power-oirposition.

As the cam-like finger 32 moves into a power-on position, the switchspring member moves in a counterclockwise direction as seen in Fig. 1.The movable contact 23 is, therefore, engaged with the stationary powerindicating contact 29. The power signal means 25 is, therefore,energized, indicating that the heating element 2d of the roaster, or thelike, is being energized or is connected to a suitable power supply. Itfollows that as the adjusting screw I4 of the thermostatic structure I8is returned to an oi position so as to deenergize or disconnect theroaster heating element, the switch spring contact arm 26 returns to acontact disengaged position so as to deenergize the power signal means(see dotted lines Fig. 1).

Adjusting screw I4 also eects the opening of the circuit to the heatingelement 24 when in the off position.

Figures 2, 6 and '1 clearly show that a shoulder exists on the screw I4,close to the end of the screw (above undercut portion I5). This shoulderpushes against bimetal I2. Therefore, as screw I4 is turned, it raisesor lowers this end of bimetal I2. When it does, the bimetal simply rocksor rotates about fulcrum I3. This changes the operating temperature ofthe thermostat because it changes the gap between the insulating pin I6and spring I1.

As screw I4 is turned counterclockwise, this gap reduces. This means thebimetal I2 has to be heated to a lower temperature than before in orderto engage spring I1 and cause contacts I9 and 23 to separate. Separationof these contacts opens heater circuit 24 in' Fig. 10, causing theroaster to cool in temperature. When it cools a few degrees, bimetal I2deects in an opposite direction to that on heating and causes contactsI9 and 23 to reclose again.

The thermostat is so designed that when screw I4 is turnedcounterclockwise, the 4operating temperature of the thermostat isreduced. As the screw I4 approaches its extreme counterclockwiseposition, it pushes on bimetal I2 with sufficient force to cause themain contacts, I9 and 23, to separate and thereby open the circuit tnthe heating element 24. Cam 32 is *so positioned on screw I4 as to startto open contacts 28 and 29 at this same instant. It does this bypressing on spring 26 as shown in Fig. 10.

A temperature signal means 31, such as an electric light, is energizedor deenergized in the following manner: The signal means 31 is connectedin series with the under-temperature contacts 35 and 36, which, at roomtemperature. are open or disengaged and the "over-temperature contacts42 and 43, which, at room temperature, are closed or engaged, as ishereinafter more fully set forth.

An under-temperature" contact arm 33 ls positioned substantially in linewith and beneath the main contact arm I1. Said arm is rigidly attachedto and insulated from the support II by means of a suitable upstandingrivet-like structure 34d. The under-temperature" contact arm 33 isformed of a resilient material and is arrangedso as to ex or be biaseddownwardly or in a clockwise direction. The under-temperature" contactarm 33 has the movable contact 35 rigidly attached to the upper surfaceof its free end portion. The free end of said contact arm 33 is locatedsubstantially above the free end of the thermally responsive element I2whereby the insulating button I6 attached thereto is adapted to engagethe lower portion of said arm. It therefore follows that, as the thermalresponsive element I2 iiexes upwardly with an increasing temperature,the insulating button I6 attached thereto and movable therewith movesthe under contact arm 33 upwardly.

The stationary under-temperature contact 36 is rigidly attached to thelower surface of the main contact arm I1 so as to be engaged by themovable under-temperature contact 35 rigidly attached to the free end ofthe undertemperature arm 33 as said arm is moved into an upper positionby the thermally responsive element I2.

.With the thermostat IU at room temperature, or at a temperaturesubstantially below that at which the thermostat is set to operate, thefree end of the thermal responsive element I2 will be in a low position.The movable end of the under-temperature contact arm 33 will accordinglybe in a low position (see Fig. 6) with the movablecontact 35v attachedthereto separated or disengaged from the stationary contact 36 carriedby the main contact arm I1. Then, as the temperature increases, thebimetallic element I2 lexes in a counterclockwise direction, moving thefree end of said element I2 upwardly.

The under-temperature contact arm 33 likewise moves upwardly in acounterclockwise direction. This movement continues until at a time justprior to the opening of the main contacts I9 and 23 when theunder-temperature movable contact 35 engages the stationaryunder-temperature" contact 36 carried by arm I1. This engagement of theunder-temperature" contacts 35 and 36 thus closes a circuit to thetemperature signal means 31, energizing said means so as to indicatethat the roaster, or the like, is at the desired operating temperature.

It follows that, with a continued movement of the bimetallic element I2,the main contact arm I1 will be likewise moved upwardly so as toseparate the main contacts I9 and 23. and deenergize the roaster heatingelement 24. A continued intermittent operation of the main elementsfollows, in keeping with established practice, so as to maintain theroaster at its predetermined temperature. However, during suchintermittent operation of the main contacts I9 and 23 and of thebimetallic element I2, the undertemperature contacts 35 and 36 remain inan engaged position.

A suitable over-temperature structure is associated with the maincontact arm I1 so as to indicate when the roaster, or the like, is at atemperature substantially above that desired. The over-temperaturestructure embodies a terminal 38 and upstanding supporting post 39, aflexible or resilient contact-carrying member 40, and an insulatedoutwardly extending fingerlike member 4I which is adapted to be engagedby the main contact arm I1. A movable contact 42 is rigidly attached tothe free end of the resilient member 40. This .movable contact 42 isadapted to engage a stationary contact 43, insulatedly attached to thesupport, during the normal operations of the thermostat I0. Theoutwardly extending finger-like member 4I extends over the main contactarm I1 and is positioned above the movable contact fastening rivet 44 soas to be engaged thereby as the arm I1 is moved to an extreme upwardposition by the thermal responsive element I2.

With such an upward movement of the main contact arm I1, the rivet 44engages the nger 4I and flexes or moves the movable contact 42 in anupward direction, disengaging the movable over-temperature contact 42from the "stationary over-temperature contact 43. This separation fromthe over-temperature" contacts deenergizes the temperature signalingmeans 31, inasmuch as the under-temperature contacts and theover-temperature contacts are in series circuit relation with saidsignaling means 31. The deenergization of the signaling means 31 thusindicates that the roaster, or the like, is not operating at or withinits predetermined temperature range. The stationary over-temperaturecontact 43 is eectrically connected to the movable under-temperaturecontact arm by means of a suitable conductor 45 insulatedly positionedon the support.

By bending or positioning the free end of the over-temperature finger 4Iwith respect to the free end of main contact arm I1 it is possible todetermine or adjust the amount of the initial over-shooting of theroaster temperature which would be permissible without deenergizing thetemperature signal 31. In other words, if desired, the signal 31 maycontinue to be energized during the initial over-shooting of the roastertemperature (see dotted line A, Fig. 9), or if desired, the signal maybe energized only within the normal temperature range for a givensetting of the thermostat (see dotted lines B and C, Fig. 9)

Referring to the accompanying drawings and particularly to the schematicwiring diagram in Fig. l0 it will be noted that as the roaster heatingelement 24 is connected to the power supply, say, at the normal roomtemperature, neither the power signal 25 nor the temperature signal 31will be energized and, inasmuch as the adjusting screw I4 of thethermostat I 0 is positioned in an off position, the heating element 24of the roaster structure, or the like, will not be energized. Then, ifit be desired to operate the roaster at a predetermined selectedtemperature value, the operator rotates the adjusting screw I4 to thedesired operating temperature. The nger or cam 32 attached to the innerportion of the adjusting screw I4 thus permits closing of the circuit tothe power indicating or signaling means 25 so as `to indicate that theroaster heating element 24 is being energized. As the temperature ofsaid roaster increases due to the energization of the heating elementthereof, the bimetallic element I2 moves in an upward direction carryingthe "under-temperature contact arm 33 upwardly therewith.

Then, just prior to the thermostat and roaster arriving at theirpredetermined temperature setting the movable "under-temperature contact35 engages the stationary "under-temperature contact 35, energizing thetemperature signaling means 31 so as to indicate that the roaster is inits predetermined set operating temperature. A continued over-shootingof the roaster temperature continues to move the bimetallic element i2in an upward direction. The insulating button I6 attached thereto thus,through the cooperation of the under-temperature" contact arm 33, andthe "under-temperature" cooperating contacts 35 and 36, bodily moves themain contact arm l1 upwardly, disengaging the main cooperating contactsI8 and 23 and deenergizing the heating element 24 of said roaster, orthe like. The roaster will then continue to be intermittently energizedin a normal manner.

If, for any reason whatsoever, as, for example. if the operator shouldlower the setting of the thermostat, said bimetaliic element I2 is movedor moves to a still further upward position, Amoving the main contactarm II further away from the main stationary contact 28, and said arm I1will engage with the "over-temperature" nger 4l, disengaging theover-temperature contacts 42 and 43. inasmuch as` the overandundert'mperature contacts are in series circuit arrangement with thetemperature signaling means 31, said temperature signaling means 31 isde energized, indicating that the'roaste'r is not at its operatingtemperature.

However, 'assuming that the roaster, or the like, decreases intemperature, said thermostatic eiement I2 will then flex or rotatedownwardly. permitting the main contact arm I1 to return to its normaloperating position or to a contact-closed position. This permits the"over-temperature" contacts 42 and 43 to be reengaged and thus permitsthe temperature signaling means 31 to be reenergized, indicating thatthe toaster, is at or within its predetermined temperature range.

It is therefore obvious that I have provided a thermostatic control fora roaster structure, or the like, which, in addition to regulating thetemperature thereof, indicates as to whether or not the roaster isconnected to a suitable power supply, and indicates as to whether or notthe roaster is operating within the preselected temperature zone, asdetermined by the operator through the adjusting means of thethermostat.

Various modiiications may be made in the detherefore that only suchlimitation shall be placed thereon as are imposed by the prior art andthe appended claim.

I claim as my invention: An electrically-heated appliance comprisingheating means, a temperature indicating signal light, and a thermostaticcontrol for said heating means and said signal light, said controlycomprising a pair of main contacts controlling said heating means, apair of under-temperature and a pair of over-temperature contactsconnected in series with each other and with said signal light forcontrolling the light, a movable arm carrying one of saidunder-temperature cont relative positions of said temperature responsivevice embodying my invention without departing from the spirit and scopethereof, and I desire means and said rst arm to vary the temperaturesetting of the control.

PAUL R. LEE.

REFERENCES. CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,393,968 Rishel Oct. 18, 19211,976,587 Teetor Oct. 9, 1934 2,074,569 Smith Mar. 23, 1937 2,151,782Lockwood Mar. 28, 1939 2,208,432 Samuels July 16, 1940 2,253,553 BurchAug. 26, 1941 2,278,629 Winning Apr. 7, 1942 2,289,882

Myers July 14, 1942

